Author: Frank Phillips
Date: 22:46:39 04/03/99
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On April 01, 1999 at 15:56:14, Andrew Williams wrote: >On April 01, 1999 at 14:37:51, Frank Phillips wrote: > >>I have added an opening book to my developing program and am wondering about >>better ways of storing the information. At the moment I store opening positions >>as a hash-table in a disk file, accessing them as I would a hash table stored in >>RAM by shifting the hash code for the appropriate number of places to generate >>the index and then performing a lookup as >>fseek(pfile,index*sizeof(record),SEEK_SET) etc. This works but involves a lot >>of wasted storage. For example, I have a 12MB file of about 1million records >>with the order of only 100 000 book entries. Is it normal having generated the >>book to then sort and search it as a simple linear file instead? What do others >>do? > >In my program, I don't store blank entries. I simply store the entries that >exist and do a binary search on the file to see if the position is in the >book. The hash key is the same as the one used in the transposition table, >but I use it in a different way. > >Andrew Thanks. I eventually used a quick sort function found on the internet which seems to work fine. As expected, my book size is now about a tenth of the one storing mainly zero. There is also no noticeable, practical difference in speed of accessing via binary search compared to hashing. Initially I tried the MSVC 5 qsort() library function but could not work out how to use the (compare) function with structures. qsort((void*) precord, records, sizeof(BookHashRecordT), compare); int __cdecl compare( const void *a, const void *b ) { /* The thing I want to sort on is in record.top32bits, where record is of type BookHashRecordT. */ return( ); } (precord is a pointer to the memory area storing the records. records the number of records.). If anybody can enlighten me I would be interested.
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